The document summarizes the pressure distribution and throughput in a vacuum system. It discusses how:
1) The lowest pressure is not in the vacuum chamber but at the inlet of the diffusion pump, and the highest pressure is at the primary pump exhaust, not at the chamber.
2) As gas moves through the system from the chamber to the primary pump, it is compressed resulting in higher pressures and lower pumping speeds. Conductance losses also reduce the effective pumping speed.
3) Keeping vacuum piping short minimizes these conductance losses to maximize the effective pumping speed available to evacuate the chamber.
This document discusses nozzles and provides objectives and information about different types of nozzles. It defines nozzles and diffusers, describes convergent and convergent-divergent nozzle shapes. It also defines critical pressure ratio and maximum mass flow, and provides equations to calculate properties like area, temperature, and velocity at different points in a nozzle. An example calculation is provided to demonstrate determining the throat and exit areas of a convergent-divergent nozzle.
1) A nozzle is a device that accelerates fluid flow by varying the cross-sectional area. Nozzles are used in applications like turbines, rockets, and jets.
2) The document discusses governing equations for nozzle flow, including the continuity and energy equations. It also covers isentropic flow assumptions.
3) Nozzle shape is examined, with convergent-divergent nozzles described as having a throat of minimum area, with subsonic flow before and supersonic after.
Critical pressure ratio, temperature ratio, velocity, and area are defined as the conditions at the throat where the velocity is sonic. An example problem is presented to demonstrate these concepts.
This document provides information about steam nozzles and steam turbines. It discusses:
1. Steam nozzles convert the heat energy of steam into kinetic energy by accelerating steam through a passage of varying cross-section.
2. Steam turbines convert the high-pressure, high-temperature steam from a steam generator into rotational shaft work.
3. There are three main types of nozzles used in steam turbines: convergent, divergent, and convergent-divergent. Convergent-divergent nozzles are widely used today.
4. The document then discusses concepts like Mach number and critical pressure that are important for steam nozzle and turbine operation.
This document discusses air compressors and their uses. It describes the main types of air compressors - reciprocating and rotary. Reciprocating air compressors operate similar to reciprocating engines, using pistons inside cylinders to compress air. Rotary air compressors compress air through the rotation of impellers or blades inside a casing. The document focuses on reciprocating air compressors and their components. It explains the operation of single-stage and two-stage reciprocating air compressors through diagrams and equations. Intercooling between stages brings the compression process closer to isothermal, reducing the work required.
Reciprocating compressors compress gases via pistons moving inside cylinders. They have high pressure pulsations and can surge if not regulated properly. Flow rate in reciprocating compressors is regulated through variable clearance volumes, variable speed, bypass valves, or suction valve unloaders. Calculating intermediate pressures in multi-stage reciprocating compressors involves determining the common pressure ratio between stages using the overall pressure ratio and number of stages.
The document discusses nozzle thermodynamics. Some key points:
1. A nozzle is a duct with varying cross-sectional area used to accelerate fluid flow through a pressure drop. Common applications include jet engines, rockets, and flow measurement.
2. Nozzle shape is determined using the steady flow energy equation. For an ideal, frictionless case the process is isentropic. Area varies to maintain constant mass flow rate.
3. The throat is the minimum cross-sectional area point. Flow is sonic at the throat for designed operating conditions. Critical pressure ratio is when sonic velocity is first reached.
4. Nozzle performance is affected by operating above or below design back pressure. Maximum
Wrong Sizing of a Reciprocating CompressorLuis Infante
Performance mapping has become a key analytical tool for the diagnostic and optimization of recip compressors, together with electronic performance analyzers. This analysis case illustrates how difficult is to operate a thermodynamically unbalanced multistage integral compressor in a borderline application. An in-house plotting routine in MS Excel (R) was used to map the basic performance (power and flow) of the individual stages across the operating range, and also to produce special-purpose maps in order to graphically depict other mechanical limits, thus helping the field operators to find (and avoid) the root cause of major troubles, including a catastrophic crankshaft failure. Mitigation and remedial cases are explored.
This document discusses net positive suction head (NPSH), which is the net pressure available at a pump's suction flange to prevent boiling. It explains how NPSH is calculated using factors like vapor pressure, atmospheric pressure, suction piping layout, and pump specifications. The document provides examples to demonstrate how these factors are incorporated into the NPSH calculation at different fluid temperatures. It emphasizes the importance of accurate NPSH calculation to avoid problems in pump operation and outlines best practices for engineers.
This document discusses nozzles and provides objectives and information about different types of nozzles. It defines nozzles and diffusers, describes convergent and convergent-divergent nozzle shapes. It also defines critical pressure ratio and maximum mass flow, and provides equations to calculate properties like area, temperature, and velocity at different points in a nozzle. An example calculation is provided to demonstrate determining the throat and exit areas of a convergent-divergent nozzle.
1) A nozzle is a device that accelerates fluid flow by varying the cross-sectional area. Nozzles are used in applications like turbines, rockets, and jets.
2) The document discusses governing equations for nozzle flow, including the continuity and energy equations. It also covers isentropic flow assumptions.
3) Nozzle shape is examined, with convergent-divergent nozzles described as having a throat of minimum area, with subsonic flow before and supersonic after.
Critical pressure ratio, temperature ratio, velocity, and area are defined as the conditions at the throat where the velocity is sonic. An example problem is presented to demonstrate these concepts.
This document provides information about steam nozzles and steam turbines. It discusses:
1. Steam nozzles convert the heat energy of steam into kinetic energy by accelerating steam through a passage of varying cross-section.
2. Steam turbines convert the high-pressure, high-temperature steam from a steam generator into rotational shaft work.
3. There are three main types of nozzles used in steam turbines: convergent, divergent, and convergent-divergent. Convergent-divergent nozzles are widely used today.
4. The document then discusses concepts like Mach number and critical pressure that are important for steam nozzle and turbine operation.
This document discusses air compressors and their uses. It describes the main types of air compressors - reciprocating and rotary. Reciprocating air compressors operate similar to reciprocating engines, using pistons inside cylinders to compress air. Rotary air compressors compress air through the rotation of impellers or blades inside a casing. The document focuses on reciprocating air compressors and their components. It explains the operation of single-stage and two-stage reciprocating air compressors through diagrams and equations. Intercooling between stages brings the compression process closer to isothermal, reducing the work required.
Reciprocating compressors compress gases via pistons moving inside cylinders. They have high pressure pulsations and can surge if not regulated properly. Flow rate in reciprocating compressors is regulated through variable clearance volumes, variable speed, bypass valves, or suction valve unloaders. Calculating intermediate pressures in multi-stage reciprocating compressors involves determining the common pressure ratio between stages using the overall pressure ratio and number of stages.
The document discusses nozzle thermodynamics. Some key points:
1. A nozzle is a duct with varying cross-sectional area used to accelerate fluid flow through a pressure drop. Common applications include jet engines, rockets, and flow measurement.
2. Nozzle shape is determined using the steady flow energy equation. For an ideal, frictionless case the process is isentropic. Area varies to maintain constant mass flow rate.
3. The throat is the minimum cross-sectional area point. Flow is sonic at the throat for designed operating conditions. Critical pressure ratio is when sonic velocity is first reached.
4. Nozzle performance is affected by operating above or below design back pressure. Maximum
Wrong Sizing of a Reciprocating CompressorLuis Infante
Performance mapping has become a key analytical tool for the diagnostic and optimization of recip compressors, together with electronic performance analyzers. This analysis case illustrates how difficult is to operate a thermodynamically unbalanced multistage integral compressor in a borderline application. An in-house plotting routine in MS Excel (R) was used to map the basic performance (power and flow) of the individual stages across the operating range, and also to produce special-purpose maps in order to graphically depict other mechanical limits, thus helping the field operators to find (and avoid) the root cause of major troubles, including a catastrophic crankshaft failure. Mitigation and remedial cases are explored.
This document discusses net positive suction head (NPSH), which is the net pressure available at a pump's suction flange to prevent boiling. It explains how NPSH is calculated using factors like vapor pressure, atmospheric pressure, suction piping layout, and pump specifications. The document provides examples to demonstrate how these factors are incorporated into the NPSH calculation at different fluid temperatures. It emphasizes the importance of accurate NPSH calculation to avoid problems in pump operation and outlines best practices for engineers.
The document discusses different types of compressors used to compress air or gas, including centrifugal, rotary, and reciprocating compressors. It then describes the operation and analysis of centrifugal and reciprocating compressors. Multistage compression is discussed as a way to increase pressure to over 300 KPa using multiple compressor stages separated by intercoolers to reduce temperature and save power compared to a single stage. The analysis shows that for ideal multistage compression with perfect intercooling, the work is equal at each stage and the total work is equal to the number of stages times the work of one stage.
The document discusses different types of compressors used to compress fluids. It classifies compressors into two main categories - rotodynamic compressors which include centrifugal and axial compressors, and positive displacement compressors which include reciprocating and rotary compressors. It then focuses on centrifugal compressors, describing their basic components like an impeller and diffuser, how they work to increase the pressure of air by accelerating it radially using an impeller before decelerating it in a diffuser, and factors affecting their gas dynamics.
This document discusses nozzles and diffusers. It defines nozzles as devices that increase velocity and decrease pressure, and defines diffusers as devices that decrease velocity and increase pressure. Equations for steady flow through nozzles and diffusers using the energy equation are presented. Convergent nozzles are used in most aircrafts while convergent-divergent nozzles are used in supersonic aircraft. The Bernoulli principle is cited to explain how pressure decreases with decreasing area while velocity increases. The conclusion compares flow quality through different nozzle types.
WATS 11 (1-50) Fluid Mechanics and ThermodynamicsMark Russell
The document describes weekly assessed tutorial sheets for fluid mechanics and thermodynamics. It provides 5 sets of practice problems for students with varying variables so each student receives unique problem values. It also provides information on resources for instructors on how to implement the weekly assessed tutorial sheet approach and contact information for the developer.
When altitude increases, water's boiling point decreases as pressure drops. For every 27mmHg increase in pressure, boiling point rises 1°C. Water vaporizes based on temperature and pressure. NPSHa is the available positive suction head, calculated as total suction head minus vapor pressure. NPSHR is the required positive suction head to avoid cavitation. Cavitation can damage pumps when NPSHa is less than NPSHR. Engineers must ensure sufficient margin between liquid and vapor states.
A multi-stage compressor compresses air or gas in two or more cylinders instead of a single cylinder to save power, limit gas discharge temperature, limit pressure differential per cylinder, and prevent issues with lubricating oil. It is common for multi-stage compressors to cool the air between stages using an intercooler. For a two-stage compressor with perfect intercooling and no pressure drops, the work of each stage is equal, the temperature is cooled back to initial levels, and the total work is equal to twice the work of one stage. For three or more stages, similar conditions apply where the work, pressures, and temperatures are equal between stages and the total work is the work of one stage multiplied by the number
This document discusses flow through nozzles used in steam turbines. It contains the following key points:
1) A nozzle converts the potential energy of steam into kinetic energy by accelerating the steam through a passage of varying cross-sectional area from high to low pressure. The velocity and specific volume of the steam increase as it expands through the nozzle.
2) Nozzles come in different shapes depending on how the velocity and specific volume change during expansion. Convergent nozzles decrease area as steam expands, while convergent-divergent nozzles first converge then diverge to match the velocity and volume changes.
3) As steam expands through the nozzle, its enthalpy decreases and this lost energy is
DESIGN AND ANALYSIS OF CONVERGENT DIVERGENT NOZZLE USING CFDNetha Jashuva
CFD is a branch of fluid mechanics that uses
numerical methods and algorithms to solve and analyze
problems that involve fluid flows. Computers are used to
perform the calculations required to simulate the interaction
of liquids and gases with surfaces defined by boundary
conditions. In this thesis, CFD analysis of flow within
Convergent-Divergent supersonic nozzle of different cross
sections rectangular, square and circular has been performed.
The analysis has been performed according to the shape of the
supersonic nozzle and keeping the same input conditions. Our
objective is to investigate the best suited nozzle which gives
high exit velocity among the different cross sections
considered. The application of these nozzles is mainly in
torpedos. The work is carried out in two stages: 1.Modeling
and analysis of flow for supersonic nozzles of different cross
sections.2.Prediction of best suited nozzle among the nozzles
considered. In this, initially modeling of the nozzles has been
done in CATIA and later on mesh generation and analysis
have been carried out in ANSYS FLUENT 14.5 and various
contours like velocity, pressure, temperature have been taken
and their variation according to different nozzles has been
studied.
Know Everything you want to know about steam nozzles(Turbine Excluded).Know more about De-Laval Nozzles and How we achieve Supersonic velocity from nozzles.Also get to know about other essentials such as Critical pressure ratio and Saturated Flow.You can use this ppt in your projects,journals.It is not copyright protected.
This document provides information about steam nozzles and turbines. It discusses the functions and types of steam nozzles, including convergent, divergent, and convergent-divergent nozzles. It also describes impulse and reaction turbines, the differences between them, and methods of compounding turbines to improve efficiency including velocity, pressure, and pressure-velocity compounding. Additionally, it covers governing methods for steam turbines using throttle, nozzle, and bypass systems to maintain a constant rotation speed under varying loads.
Surge occurs when the pressure behind a centrifugal compressor becomes higher than the outlet pressure, causing fluid to reverse flow into the compressor. This unstable phenomenon repeats in cycles around 1-2 Hz. To prevent surge, anti-surge control systems detect when the operating point approaches the surge line and open a recycle valve to increase inlet flow and move the operating point away from the surge line. Proportional-integral and proportional-integral-derivative algorithms are commonly used to control the recycle valve based on differences between the process variable and set point.
Air Compressor in mechanical EngineeringNayan Dagliya
The document discusses different types of compressors and their applications. It begins by explaining that a compressor takes in atmospheric air, compresses it, and delivers high-pressure air to a storage vessel. It then describes two basic compressor types - positive displacement compressors that mechanically reduce air volume to increase pressure, and dynamic compressors that impart velocity energy to continuously flowing air. Specific compressor types are then outlined, including reciprocating compressors that use pistons, rotary vane compressors with rotating blades, and screw compressors that employ two rotating helical screws to compress air. Applications of compressed air in tools, spraying, mining, and pneumatic systems are also summarized.
- Radiators are heat exchangers used to remove heat from engines and propulsion systems. Their design considers thermal performance, size constraints, and pressure drops.
- A radiator's thermal performance depends on parameters like mass flow rates, temperatures, heat transfer coefficients, and surface area. Its total surface area can be calculated using these parameters and equations from the first law of thermodynamics.
- An example calculation shows determining the surface area of a double pipe radiator given inlet/outlet temperatures, mass flow rates, heat capacities, and heat transfer coefficients. Assumptions like negligible wall resistance are made to simplify the early design stage calculations.
The document provides specifications and information about pump head, peripheral velocity, suction lift, static and total heads, friction head, velocity head, pressure head, net positive suction head (NPSH), pump curves, affinity laws, and materials. Key parameters discussed include head, flow rate, speed, impeller diameter, suction lift, static and total heads, NPSH available and required. Conversion factors and equations for calculating head, flow, power and NPSH are also presented.
The document provides details on the design process for a centrifugal pump given specific head, flow rate, and speed requirements provided by the client. Key steps include:
1) Calculating hydraulic parameters like flow rate, horsepower required, and shaft torque to size the shaft diameter.
2) Designing dimensions of the impeller like eye diameter, inlet and outlet angles, and widths to achieve the required flow while minimizing leakage losses.
3) Iteratively adjusting dimensions like impeller diameter until the calculated head matches the specified head within an acceptable tolerance.
The document discusses different types of nozzles used in steam turbines, including convergent, divergent, and convergent-divergent nozzles. It summarizes thermal modeling and analysis that was conducted to compare the erosion rates of three nozzle types: Moore nozzle, Moses and Stein nozzle, and convergent-divergent nozzle. The analysis found that the convergent-divergent nozzle had the highest velocity and comparatively minimum erosion rate, making it the best performing of the three nozzle types.
This document provides information about air compressors, including reciprocating and rotary compressors. It discusses single stage and two stage reciprocating compressors, detailing their workings using pressure-volume diagrams. It also covers testing methods, classifications, and efficiency parameters for compressors. Rotary compressor types like screw, vane, and lobe compressors are introduced as well.
The document discusses axial flow compressors. It begins with an overview that axial flow compressors have multiple stages, each with a row of rotor blades followed by a row of stator blades. The fluid is accelerated by the rotor blades and decelerated in the stator, converting kinetic to static pressure energy. Due to small pressure increases per stage, axial compressors require many stages. The document then provides details on the elementary theory, velocity triangles, degree of reaction, and three dimensional flow effects in axial compressors. It concludes with discussing the design process which includes choosing operating parameters, determining number of stages, calculating air angles, and testing.
Centrifugal pumps work by using an impeller attached to a rotating shaft to move liquid from the pump inlet to the discharge outlet. As the impeller spins, it creates lower pressure at the center to draw liquid in and higher pressure at the outer edge to push liquid out.
When selecting a pump, the key parameters are capacity (flowrate) and total head. Total head considers the static head from elevation changes as well as friction, pressure, and velocity heads from piping, valves, and changes in pressure or speed of the liquid. The specific gravity of the liquid affects the pressure but not the total head required from the pump.
This document summarizes key concepts related to nozzles, including:
1) The critical velocity is the sonic velocity reached at the throat of a convergent-divergent nozzle when the pressure ratio across the nozzle equals the critical pressure ratio.
2) The maximum mass flow rate through a nozzle occurs when the pressure at the throat equals the critical pressure.
3) Nozzles can be convergent, convergent-divergent, or convergent with shock waves inside or outside depending on the pressure ratio across the nozzle.
1. The lecture discusses key concepts related to vacuum including why vacuum is necessary, why a perfect vacuum cannot be created, and definitions of molecular density, mean free path, and time for monolayer formation that characterize different degrees of vacuum.
2. Vacuum is necessary to provide a clean environment, reduce atmospheric loads, offer moisture-free conditions, decrease particle flux, and control processes.
3. A perfect vacuum with absolute zero pressure cannot be achieved due to black-body radiation from vacuum chamber walls, outgassing of materials, and limitations of vacuum pump technology.
The document discusses different types of compressors used to compress air or gas, including centrifugal, rotary, and reciprocating compressors. It then describes the operation and analysis of centrifugal and reciprocating compressors. Multistage compression is discussed as a way to increase pressure to over 300 KPa using multiple compressor stages separated by intercoolers to reduce temperature and save power compared to a single stage. The analysis shows that for ideal multistage compression with perfect intercooling, the work is equal at each stage and the total work is equal to the number of stages times the work of one stage.
The document discusses different types of compressors used to compress fluids. It classifies compressors into two main categories - rotodynamic compressors which include centrifugal and axial compressors, and positive displacement compressors which include reciprocating and rotary compressors. It then focuses on centrifugal compressors, describing their basic components like an impeller and diffuser, how they work to increase the pressure of air by accelerating it radially using an impeller before decelerating it in a diffuser, and factors affecting their gas dynamics.
This document discusses nozzles and diffusers. It defines nozzles as devices that increase velocity and decrease pressure, and defines diffusers as devices that decrease velocity and increase pressure. Equations for steady flow through nozzles and diffusers using the energy equation are presented. Convergent nozzles are used in most aircrafts while convergent-divergent nozzles are used in supersonic aircraft. The Bernoulli principle is cited to explain how pressure decreases with decreasing area while velocity increases. The conclusion compares flow quality through different nozzle types.
WATS 11 (1-50) Fluid Mechanics and ThermodynamicsMark Russell
The document describes weekly assessed tutorial sheets for fluid mechanics and thermodynamics. It provides 5 sets of practice problems for students with varying variables so each student receives unique problem values. It also provides information on resources for instructors on how to implement the weekly assessed tutorial sheet approach and contact information for the developer.
When altitude increases, water's boiling point decreases as pressure drops. For every 27mmHg increase in pressure, boiling point rises 1°C. Water vaporizes based on temperature and pressure. NPSHa is the available positive suction head, calculated as total suction head minus vapor pressure. NPSHR is the required positive suction head to avoid cavitation. Cavitation can damage pumps when NPSHa is less than NPSHR. Engineers must ensure sufficient margin between liquid and vapor states.
A multi-stage compressor compresses air or gas in two or more cylinders instead of a single cylinder to save power, limit gas discharge temperature, limit pressure differential per cylinder, and prevent issues with lubricating oil. It is common for multi-stage compressors to cool the air between stages using an intercooler. For a two-stage compressor with perfect intercooling and no pressure drops, the work of each stage is equal, the temperature is cooled back to initial levels, and the total work is equal to twice the work of one stage. For three or more stages, similar conditions apply where the work, pressures, and temperatures are equal between stages and the total work is the work of one stage multiplied by the number
This document discusses flow through nozzles used in steam turbines. It contains the following key points:
1) A nozzle converts the potential energy of steam into kinetic energy by accelerating the steam through a passage of varying cross-sectional area from high to low pressure. The velocity and specific volume of the steam increase as it expands through the nozzle.
2) Nozzles come in different shapes depending on how the velocity and specific volume change during expansion. Convergent nozzles decrease area as steam expands, while convergent-divergent nozzles first converge then diverge to match the velocity and volume changes.
3) As steam expands through the nozzle, its enthalpy decreases and this lost energy is
DESIGN AND ANALYSIS OF CONVERGENT DIVERGENT NOZZLE USING CFDNetha Jashuva
CFD is a branch of fluid mechanics that uses
numerical methods and algorithms to solve and analyze
problems that involve fluid flows. Computers are used to
perform the calculations required to simulate the interaction
of liquids and gases with surfaces defined by boundary
conditions. In this thesis, CFD analysis of flow within
Convergent-Divergent supersonic nozzle of different cross
sections rectangular, square and circular has been performed.
The analysis has been performed according to the shape of the
supersonic nozzle and keeping the same input conditions. Our
objective is to investigate the best suited nozzle which gives
high exit velocity among the different cross sections
considered. The application of these nozzles is mainly in
torpedos. The work is carried out in two stages: 1.Modeling
and analysis of flow for supersonic nozzles of different cross
sections.2.Prediction of best suited nozzle among the nozzles
considered. In this, initially modeling of the nozzles has been
done in CATIA and later on mesh generation and analysis
have been carried out in ANSYS FLUENT 14.5 and various
contours like velocity, pressure, temperature have been taken
and their variation according to different nozzles has been
studied.
Know Everything you want to know about steam nozzles(Turbine Excluded).Know more about De-Laval Nozzles and How we achieve Supersonic velocity from nozzles.Also get to know about other essentials such as Critical pressure ratio and Saturated Flow.You can use this ppt in your projects,journals.It is not copyright protected.
This document provides information about steam nozzles and turbines. It discusses the functions and types of steam nozzles, including convergent, divergent, and convergent-divergent nozzles. It also describes impulse and reaction turbines, the differences between them, and methods of compounding turbines to improve efficiency including velocity, pressure, and pressure-velocity compounding. Additionally, it covers governing methods for steam turbines using throttle, nozzle, and bypass systems to maintain a constant rotation speed under varying loads.
Surge occurs when the pressure behind a centrifugal compressor becomes higher than the outlet pressure, causing fluid to reverse flow into the compressor. This unstable phenomenon repeats in cycles around 1-2 Hz. To prevent surge, anti-surge control systems detect when the operating point approaches the surge line and open a recycle valve to increase inlet flow and move the operating point away from the surge line. Proportional-integral and proportional-integral-derivative algorithms are commonly used to control the recycle valve based on differences between the process variable and set point.
Air Compressor in mechanical EngineeringNayan Dagliya
The document discusses different types of compressors and their applications. It begins by explaining that a compressor takes in atmospheric air, compresses it, and delivers high-pressure air to a storage vessel. It then describes two basic compressor types - positive displacement compressors that mechanically reduce air volume to increase pressure, and dynamic compressors that impart velocity energy to continuously flowing air. Specific compressor types are then outlined, including reciprocating compressors that use pistons, rotary vane compressors with rotating blades, and screw compressors that employ two rotating helical screws to compress air. Applications of compressed air in tools, spraying, mining, and pneumatic systems are also summarized.
- Radiators are heat exchangers used to remove heat from engines and propulsion systems. Their design considers thermal performance, size constraints, and pressure drops.
- A radiator's thermal performance depends on parameters like mass flow rates, temperatures, heat transfer coefficients, and surface area. Its total surface area can be calculated using these parameters and equations from the first law of thermodynamics.
- An example calculation shows determining the surface area of a double pipe radiator given inlet/outlet temperatures, mass flow rates, heat capacities, and heat transfer coefficients. Assumptions like negligible wall resistance are made to simplify the early design stage calculations.
The document provides specifications and information about pump head, peripheral velocity, suction lift, static and total heads, friction head, velocity head, pressure head, net positive suction head (NPSH), pump curves, affinity laws, and materials. Key parameters discussed include head, flow rate, speed, impeller diameter, suction lift, static and total heads, NPSH available and required. Conversion factors and equations for calculating head, flow, power and NPSH are also presented.
The document provides details on the design process for a centrifugal pump given specific head, flow rate, and speed requirements provided by the client. Key steps include:
1) Calculating hydraulic parameters like flow rate, horsepower required, and shaft torque to size the shaft diameter.
2) Designing dimensions of the impeller like eye diameter, inlet and outlet angles, and widths to achieve the required flow while minimizing leakage losses.
3) Iteratively adjusting dimensions like impeller diameter until the calculated head matches the specified head within an acceptable tolerance.
The document discusses different types of nozzles used in steam turbines, including convergent, divergent, and convergent-divergent nozzles. It summarizes thermal modeling and analysis that was conducted to compare the erosion rates of three nozzle types: Moore nozzle, Moses and Stein nozzle, and convergent-divergent nozzle. The analysis found that the convergent-divergent nozzle had the highest velocity and comparatively minimum erosion rate, making it the best performing of the three nozzle types.
This document provides information about air compressors, including reciprocating and rotary compressors. It discusses single stage and two stage reciprocating compressors, detailing their workings using pressure-volume diagrams. It also covers testing methods, classifications, and efficiency parameters for compressors. Rotary compressor types like screw, vane, and lobe compressors are introduced as well.
The document discusses axial flow compressors. It begins with an overview that axial flow compressors have multiple stages, each with a row of rotor blades followed by a row of stator blades. The fluid is accelerated by the rotor blades and decelerated in the stator, converting kinetic to static pressure energy. Due to small pressure increases per stage, axial compressors require many stages. The document then provides details on the elementary theory, velocity triangles, degree of reaction, and three dimensional flow effects in axial compressors. It concludes with discussing the design process which includes choosing operating parameters, determining number of stages, calculating air angles, and testing.
Centrifugal pumps work by using an impeller attached to a rotating shaft to move liquid from the pump inlet to the discharge outlet. As the impeller spins, it creates lower pressure at the center to draw liquid in and higher pressure at the outer edge to push liquid out.
When selecting a pump, the key parameters are capacity (flowrate) and total head. Total head considers the static head from elevation changes as well as friction, pressure, and velocity heads from piping, valves, and changes in pressure or speed of the liquid. The specific gravity of the liquid affects the pressure but not the total head required from the pump.
This document summarizes key concepts related to nozzles, including:
1) The critical velocity is the sonic velocity reached at the throat of a convergent-divergent nozzle when the pressure ratio across the nozzle equals the critical pressure ratio.
2) The maximum mass flow rate through a nozzle occurs when the pressure at the throat equals the critical pressure.
3) Nozzles can be convergent, convergent-divergent, or convergent with shock waves inside or outside depending on the pressure ratio across the nozzle.
1. The lecture discusses key concepts related to vacuum including why vacuum is necessary, why a perfect vacuum cannot be created, and definitions of molecular density, mean free path, and time for monolayer formation that characterize different degrees of vacuum.
2. Vacuum is necessary to provide a clean environment, reduce atmospheric loads, offer moisture-free conditions, decrease particle flux, and control processes.
3. A perfect vacuum with absolute zero pressure cannot be achieved due to black-body radiation from vacuum chamber walls, outgassing of materials, and limitations of vacuum pump technology.
Mass spectrometry is an analytical technique that identifies unknown compounds by converting sample molecules into ions, characterizing them by their mass-to-charge ratio (m/z), and measuring relative abundances. It works by ionizing samples, separating the ions based on m/z using an analyzer, and detecting the ions using a detector. The instrument consists of an ion source, analyzer, and detector system, and operates by producing ions, separating them by m/z, and detecting abundances to produce mass spectra that provide structural information about molecules.
There are three main mechanisms that contribute to creep in metals:
1) Dislocation slip and climb, where dislocations move through the crystal lattice with the aid of vacancies allowing them to climb past obstacles.
2) Grain boundary sliding, where shear stresses cause grain boundaries to slide past one another.
3) Diffusional flow, where atoms diffuse from high stress areas to low stress areas within grains or along grain boundaries, elongating the material. Each mechanism involves the thermally activated movement of vacancies within the metal.
Stainless steel is a corrosion-resistant steel that contains at least 10% chromium. The chromium forms a thin, protective oxide film on the steel's surface. There are several types of stainless steel classified by their chromium and other elemental contents. Producing stainless steel from an electric arc furnace alone is difficult because it requires very high temperatures to remove carbon without excessively oxidizing chromium from the melt. Solutions include increasing temperature to favor carbon removal over chromium oxidation and adding ferroalloys to recover oxidized chromium and adjust alloy content.
The document discusses temperature profiles for liquid steel in ladles and tundishes. It states that steel temperatures change over time and the goal is to order ladles with the right temperatures. Temperatures that are too low risk solidification and temperatures that are too high can adversely affect strand quality, refractory wear, and heating costs. The document also discusses misalignment strains that can occur from misaligned rolls in continuous casting, which can be tensile or compressive depending on the misalignment direction.
Positive displacement pumps work by trapping a fixed amount of gas or fluid and forcing it into the discharge pipe using mechanical movements like rotary vanes or diaphragms. Momentum transfer pumps use high velocity streams or fast moving surfaces to transfer gas molecules to an outlet at a lower pressure through interactions. Capture pumps remove molecules from the gas phase by trapping them on surfaces using condensation or adsorption, with no pump outlet, as in cryogenic, sublimation, or ion pumps where electric or magnetic fields aid the capture process.
The document discusses the process of deoxidizing steel. During steelmaking, oxygen dissolves into the liquid steel but not in the solid steel. Deoxidation or "killing" of steel refers to reducing the excess oxygen content before casting to prevent blowholes and inclusions. This is typically done through precipitation deoxidation using elements like aluminum, silicon, and manganese that have a higher affinity for oxygen than iron and form stable oxides. These deoxidizers are chosen based on factors like stability, deoxidizing ability, oxide melting point and density. Aluminum is the most powerful deoxidizer but its oxide alumina must be modified to remain liquid during casting.
This document provides an overview of key concepts in vacuum physics and technology. It discusses the kinetic molecular theory, which explains gas particle behavior at low pressures. It defines the Knudsen number for characterizing different flow regimes from viscous to molecular flow. It also describes various surface interactions that can occur when gas molecules contact surfaces, such as adsorption, backscattering, and desorption. Finally, it explains the phenomena of outgassing, in which trapped gases are released from surfaces over time, and permeation, where gases can diffuse through some solid materials.
The document introduces metal forming processes. It defines metal forming as shaping metallic materials through plastic deformation, where the shape changes permanently in contrast to elastic deformation. It describes bulk deformation processes as involving large plastic deformation without changing volume. These include hot working like forging above the recrystallization temperature for easier forming, and cold working like rolling at room temperature for better accuracy. Sheet forming processes change the shape but not the cross-section, operating on thin metal sheets using stamping presses.
Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.
The document discusses techniques for analyzing materials that have fractured. Chemical analysis can identify deviations from specifications, impurities, and corrosion products. Mechanical testing determines if the material's properties met standards and withstood stresses. Nondestructive evaluation techniques like ultrasonics, radiography, and eddy currents detect subsurface flaws without destroying the component. Together, these analyses provide information about what caused the material to fracture.
1) The document discusses various defects that can occur during steel ingot solidification such as pipe, columnar structure, blow holes, and segregation.
2) It provides remedies for preventing these defects, such as using a hot top feeder head to avoid pipe formation and soaking ingots to minimize segregation.
3) The document also covers the mechanisms of ingot solidification, describing how killed, rimmed, and semi-killed steels solidify into chill, columnar, and equiaxed zones within the ingot.
Continuous casting is a steelmaking process where liquid steel is solidified into a semi-finished billet, bloom, or slab. In this process, liquid steel flows from a ladle into a water-cooled copper mold. As the steel exits the mold, it begins to solidify on the surface while the core remains liquid. The semi-solid steel strand is then cooled further through water sprays to fully solidify it into the desired cross-section. The continuous casting process allows for higher productivity and quality than traditional ingot casting.
Vacuum degassing is commonly used in steel production to remove gases like hydrogen and nitrogen from liquid steel. It works by exposing the steel to vacuum conditions, which allows the gases to be readily removed. Specifically, vacuum degassing lowers the levels of dissolved gases to parts per million and improves the quality of the final cast product by preventing cracking defects. It is a critical process that improves both productivity and quality in continuous steel casting.
Secondary steel making processes are used to further refine special steels produced through primary steel making. These secondary processes are critical for achieving stringent quality requirements for cleanliness, grain size, and hardenability in steels used for applications like aircraft components and pipelines. Various furnaces and techniques can be used for secondary refining, including ladle furnaces, argon oxygen decarburization, vacuum treatments, and stirring to homogenize temperature and composition and accelerate inclusion removal from the steel. Stirring is commonly done by bubbling gas through the steel bath via submerged lances or porous plugs, or using electromagnetic stirring.
This document outlines the course plan for a steel making processes course. It includes topics that will be covered such as the various steelmaking methods like basic oxygen furnace and electric arc furnace. It also lists the textbook references and learning resources provided. The course will have lectures, assignments, simulations, midterm and final exams. Students will learn about the raw materials, chemistry, equipment and processes involved in steel production.
This document provides information about induced draft fans and false air calculation at a cement plant. It discusses the types of fans used, including centrifugal and axial fans. It describes the basic fan laws around how fan performance is affected by speed, air density, and diameter. The document outlines the common equipment used for measurements. It provides the calculations for density, velocity, volumetric air flow, pressure, power, and efficiency. Finally, it discusses ways to improve fan performance and minimize false air in ducts.
This document discusses various types of air ducts and factors to consider in duct system design such as space availability and noise levels. Ducts are usually made of galvanized iron or aluminum sheet metal and can be circular, rectangular, or square. Circular ducts are preferred economically. Airflow in ducts is produced by pressure differences between locations. Pressure losses occur due to friction and changes in duct geometry. Common duct design methods include the velocity method, equal pressure drop method, and static regain method which aim to select appropriate duct dimensions and fan pressure.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
There are three types of injection systems used with reciprocating internal combustion engines: 1) inlet-port injection, 2) early cylinder injection, and 3) later cylinder injection. Injection systems for diesel engines are all of type 3, which involves late injection of fuel directly into the cylinder near top center. These systems require high injection pressures, ranging from 2000 to over 20,000 psi, to achieve finely divided sprays for rapid mixing with air at high compression densities. Fuel injection systems are characterized by metering, or supplying the desired quantity of fuel, and spray formation, or controlling the physical characteristics of the spray. The two main methods of fuel metering are the common rail system and the jerk pump system.
This document provides an overview of different types of steam turbines used in maritime applications. It discusses the basic design and operation of impulse turbines, impulse-reaction turbines, and pressure compounded turbines. Impulse turbines only utilize changes in steam direction to turn the turbine, while impulse-reaction turbines also utilize pressure drops across the blades. Pressure compounded turbines split the overall pressure drop into multiple smaller stages to reduce steam velocities to practical levels for ship propulsion. The document also covers nozzle design and how it controls the expansion of steam to convert heat energy to kinetic energy for driving the turbine.
This document provides an overview of duct sizing and design principles for HVAC systems. It discusses key topics such as duct components, materials, classifications, sizing methods, pressure losses, fan sizing, supply and return duct systems, fittings, construction practices, insulation, noise control, testing and balancing, and cleaning. The document emphasizes that properly designed ductwork is essential for an HVAC system to function effectively and provide optimal comfort, efficiency and indoor air quality.
This document provides information and equations for calculating the flow capacity (Cv) of control valves for liquid, gas, and two-phase flow. It defines Cv as the flow in gallons per minute through a valve with a one psi pressure drop. It describes how to calculate Cv for liquids and gases using factors like pressure recovery, critical pressure ratio, Reynolds number, and piping geometry. Guidelines are given for maximum recommended flow velocities depending on the type of fluid.
We live in the 21. century, we drive cars, we have the thermal and nuclear power plants and it all started with the work of Carnot, who established the principle of creating work of en engine from the supplied warmth. However, we have also problems with the pollution of our environment and the created warmth from these technical devices
1) The document discusses a new proposed engine design that uses the spontaneous transfer of compressed air from the engine cylinder to an absorber chamber to reduce the mass of air compressed and thereby reduce the work of compression.
2) It then goes through the thermodynamic cycle calculations to show that the work of expansion is greater than the reduced work of compression, resulting in a net work output to produce power.
3) The author estimates that a four cylinder version of this new engine could produce 23 kW of power, and would be more efficient and not pollute the environment like current fuel-burning engines.
The document discusses various methods for measuring fluid flow, including differential pressure flow meters, velocity flow meters, positive displacement flow meters, and open channel flow meters. It provides details on some common differential pressure flow meter technologies like orifice plates and pitot tubes. An orifice plate works by measuring the differential pressure across the plate to calculate flow rate, while a pitot tube measures the difference between stagnation and static pressures to determine fluid velocity at a point. The document also explains factors to consider in selecting a flow measurement approach and classifies meters as either primary quantity meters or secondary rate meters.
The document describes an experiment to determine the volumetric efficiency of an air compressor at different speeds and pressures. It provides background on compressors and defines volumetric efficiency. The procedures, calculations, results and analysis are presented. Key findings include that volumetric efficiency varies with load and speed, is reduced from theoretical by clearance volume, and is affected by factors like induction/exhaust friction. Suggestions to minimize errors in the experiment are also provided.
Stall can most easily be defined as a condition in which heat transfer equipment is unable to drain condensate and becomes flooded due to insufficient system pressure.
What causes stall?
Stall occurs primarily in heat transfer equipment where the steam pressure is modulated to obtain a desired output (i.e. product temperature). The pressure range of any such equipment ( coils, shell & tube, etc....) can be segmented into two (2) distinct operational modes: Operating and Stall
Operating: In the upper section of the pressure range the operating pressure (OP) of the equipment is greater than the back pressure (BP) present at the discharge of the steam trap. Therefore a positive pressure differential across the trap exists allowing for condensate to flow from the equipment to the condensate return line.
Stall: In the lower section of the pressure range the operating pressure (OP) of the equipment is less than or equal to the back pressure (BP) present at the discharge of the steam trap. Therefore a negative or no pressure differential exists, this does not allow condensate to be discharged to the return line and the condensate begins to collect and flood the equipment.
This document provides an overview of Module 5 of a Process Engineering Training Program on fan measurement and testing. The module covers topics such as fan pressure, fan curves, fan laws, controlling fan output, unsatisfactory fan performance, series fans, parallel fans, blade types, fan noise, and other gas pumping equipment. It includes definitions of key fan terms, equations, diagrams of fan setups and performance, and factors that affect fan operation. The module aims to teach trainees how to measure, analyze, and optimize the performance of industrial fans used in chemical processes.
This document discusses pneumatic and electro-pneumatic systems. It covers the objectives of studying these topics which are to provide knowledge of fluid power applications in industry and an understanding of pneumatic components. The document then describes various pneumatic system elements like compressors, filters, regulators, lubricators and valves. It also explains the properties of air and perfect gas laws. Finally, it discusses pneumatic circuits and the cascade method for designing circuits.
One of the most popular methods of moving solids in the chemical industry is pneumatic conveying. Pneumatic conveying refers to the moving of solids suspended in or forced by a gas stream through horizontal and/or vertical pipes. Pneumatic conveying can be used for particles ranging from fine powders to pellets and bulk densities of 16 to 3200 kg/m3 (1 to 200 lb/ft3).
This document discusses duct design for HVAC systems. It defines different types of ducts including supply, return, fresh air, and exhaust ducts. It also covers duct classification based on velocity and pressure, duct shapes, sizing methods like equal friction and static regain, and standard duct sizes for different air flows. Design considerations include aspect ratio, static versus dynamic pressure, and pressure losses from friction and changes in air flow.
The document provides an overview of compressors and compressed air systems. It discusses the different types of compressors, including reciprocating, rotary, screw, and centrifugal compressors. Reciprocating compressors use pistons to compress air in single or multiple stages. They are suitable for applications requiring low flow rates and high pressure. The document also discusses compressed air ratings like SCFM and ACFM, and how to properly size compressed air systems based on conditions like pressure, temperature, and humidity.
The document discusses flowmetering steam. It begins by quoting Lord Kelvin about the importance of measurement. Many businesses now recognize the value of energy cost accounting, conservation, and monitoring techniques using tools like flowmetering. Steam is difficult to measure accurately. Flowmeters designed for liquids and gases don't always work well for steam. The document then discusses fundamentals of fluid mechanics including density, viscosity, Reynolds number, and flow regimes as they relate to measuring steam flow. Accurately measuring steam use allows optimizing plant efficiency and energy efficiency through monitoring steam demand and identifying major steam users.
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This document discusses the development of bulk nanocrystalline steel. Previous attempts to create ultra-strong materials by decreasing crystal size were limited by strength reductions as size increased due to more defects. A new method is proposed using carbide-free bainite transformation which is displacive and can generate very fine grains down to 10 nanometers. This bainitic transformation meets the design criteria of allowing large components, ultra-fine grain size, and low-cost production method required for bulk nanocrystalline steel.
1. Martensite forms via a diffusionless, displacive transformation in which the crystal structure changes rapidly without atomic diffusion.
2. The interface between austenite and martensite, called the habit plane, must be semi-coherent to allow rapid transformation. It consists of a set of dislocations that provide continuity between the crystals.
3. Martensitic transformation results in both a crystal structure change and a shape deformation of the material, as observed using interference microscopy techniques. The shape change is caused by a combination of volume expansion during the structure change coupled with simple shear deformation.
1) Phase transformations in solid metals include the decomposition of austenite into other phases such as bainite, Widmanstätten ferrite, and acicular ferrite.
2) Bainite forms by the decomposition of austenite at a temperature above the martensite start temperature but below the temperature at which fine pearlite forms.
3) Widmanstätten ferrite nucleates from austenite grain boundaries and grows in a displacive mechanism, maintaining an atomic correspondence between the parent and product phases resulting in a triangular shape.
4) Acicular ferrite forms as thin plates within prior austenite grains or as sideplates from grain boundaries
The document discusses phase transformations in solid metals and alloys. It provides contact information for Dr. Muhammad Ali Siddiqui of NED University of Pakistan who teaches a course on this topic. It then lists several recommended textbooks on phase transformations and diagrams before outlining the topics that will be covered in the lecture series, including diffusion mechanisms, phase diagrams, and the classification of phase transformations.
The document discusses various corrosion testing techniques presented by Dr. Muhammad Ali Siddiqui of NED University of Engineering and Technology in Karachi, Pakistan. It describes open circuit potential (OCP) measurements, linear polarization resistance (LPR) testing, and potentiodynamic polarization measurements (PDMs). LPR uses the slope of the potential-current plot near corrosion potential to determine polarization resistance and corrosion rate. PDMs involve sweeping the potential from active to passive regions to obtain corrosion current, potentials, and characteristics of passive films. The document provides experimental procedures, examples, and data analysis for these electrochemical corrosion testing methods.
This document discusses corrosion engineering and corrosion testing. It begins with introductions to corrosion science and corrosion engineering. It then discusses the responsibilities of corrosion engineers, including ensuring safety and minimizing economic losses from corrosion. Direct economic losses include replacing corroded structures, while indirect losses include shutdowns and loss of efficiency. The document also summarizes various examples of corrosion, classifies corrosion into wet and dry types, and explains corrosion as an electrochemical reaction. It describes equipment used for corrosion testing like electrochemical workstations and defines key terms like potential and current. Finally, it discusses open circuit potential graphs used in corrosion testing.
1. Slag is a molten oxide byproduct formed during smelting and refining of metals like steel. It contains both acidic oxides like SiO2 and basic oxides like CaO that neutralize each other.
2. An ideal slag for steelmaking has a basicity between 1.2-2.5, is sufficiently fluid, and can act as a thermal barrier while controlling the oxidation state of the steel through its FeO content.
3. The basicity, viscosity, oxidation potential, and ability to hold inclusions determine a slag's efficiency in refining steel of non-metallic impurities like phosphorus and sulfur.
The document summarizes a case study of the failure of a low-pressure turbine rotor (LPTR) blade in a jet engine. Visual examination found a fatigue crack had initiated at the leading edge of the blade and propagated about 1 mm intergranularly and then about 11 mm transgranularly. Testing showed the microstructure at the leading edge had experienced dissolution of gamma prime precipitates, reducing the hardness and creep resistance. The failure mechanism involved initial stress rupture cracking at the leading edge followed by fatigue crack propagation. High operating temperatures caused the failure by dissolving precipitates and degrading the blade's strength properties.
This presentation summarizes the history of traditional Chinese clothing over different dynasties from 2100 BC to 1900 AD. It discusses the basic styles and materials used in each major dynasty, including the Xia, Shang, Zhou, Qin, Han, Tang and Song dynasties. Key points covered include the introduction of silk during the Xia dynasty, the basic blouse and skirt combination created in Shang/Zhou, standardized black clothing in Qin, specific colors assigned to ranks in Han, and the luxurious, revealing styles of Tang dynasty clothing made primarily of silk. The presentation provides an overview of the evolution of traditional Chinese fashion and materials over thousands of years of Chinese history.
This document provides an overview of the methodology for conducting failure analysis of materials and components. It discusses collecting background information on the failed component and failure details. Key steps in the process include examining the failure site, documenting locations, collecting specimen samples, performing laboratory tests, analyzing test data, and preparing a report detailing the root cause failure mechanism. The methodology is a multidisciplinary approach requiring expertise across various engineering domains to properly analyze failures and prevent future occurrences.
The document outlines the methodology for conducting a failure analysis, including collecting background information on the failed component, examining the failure site, taking specimens for laboratory testing, analyzing test data, and preparing a report documenting the sequence of events leading to failure and providing recommendations. The process is multidisciplinary and aims to determine the root cause of failure through a systematic approach involving visual inspection, metallurgical examination, and mechanical testing of specimens from the failed component.
This document discusses the development of bulk nanocrystalline steel with exceptionally high strength. It describes how bainite formation through isothermal or continuous cooling transformation can produce a nanocrystalline microstructure in steel. A specific alloy composition is presented that achieves a nanocrystalline microstructure with 20-40nm thick ferrite plates after transforming at 200C for 10 days. This results in an ultrahigh strength of 2.5GPa but maintains good ductility. The technique allows large component manufacturing and is cost effective.
1. The document discusses the Schaeffler diagram, which is used to predict the microstructure of stainless steel welds based on their composition. It also discusses modifications to the diagram by Delong.
2. The M3 concept for developing third generation advanced high strength steels is described, which aims to achieve ultrahigh strength and ductility through a multi-phase, meta-stable, multi-scale microstructure.
3. Quenching and partitioning heat treatments are summarized as a novel method to produce multi-phase steels with significant retained austenite through quenching to form martensite and austenite, followed by an isothermal treatment to partition carbon into the a
1. Diffusion is the transport of atoms or molecules in solids, liquids, or gases due to a gradient in concentration or pressure. In solids, atoms constantly vibrate but bonds prevent long-range motion except through defects like vacancies.
2. There are two main diffusion mechanisms in solids - vacancy diffusion, where an atom hops into an adjacent vacant lattice site, and interstitial diffusion, where a small atom squeezes through spaces in the host lattice. Diffusion requires thermal energy to break bonds and depends strongly on temperature.
3. Fick's laws describe diffusion - the flux is proportional to the concentration gradient according to Fick's first law, and the rate of change of concentration
The document discusses phase transformations in solids. It defines phases as homogeneous regions of a material that are physically distinct. Phase transformations occur when an initial state becomes unstable relative to a final state. The stability of a system is determined by its Gibbs free energy (G), which depends on enthalpy (H), entropy (S), temperature (T), and pressure (P). Binary phase diagrams illustrate the phases present at various compositions and temperatures. Common diagram types include eutectic systems where components are soluble in liquid but not solid, and partially soluble solid systems. Determining phase amounts uses the lever rule based on composition and phase boundaries.
Austenitic iron is non-magnetic, while ferritic iron is magnetic, due to their different temperatures rather than phases. Magnetism in iron arises from electron spin alignment within atomic zones. Above the Curie temperature, thermal energy disrupts zone formation, eliminating magnetism. The Curie point for iron is near austenite's stability range, but heating ferrite or quenching austenite above the Curie point also removes magnetism, demonstrating it is a temperature not phase effect.
The document discusses creep and stress rupture behavior of materials at high temperatures. It provides an introduction to creep and stress rupture tests, describing the three stages of creep curves and how applied stress and temperature affect creep behavior. Different deformation mechanisms at high temperatures are discussed, including dislocation glide/creep, diffusion creep, and grain boundary sliding. The document also covers topics such as structural changes during creep, superplasticity, and fracture modes at elevated temperatures.
This document discusses fractography, which is the analysis of fracture surfaces. It begins by defining fractography and distinguishing between macrofractography and microfractography. Macrofractography examines fracture surfaces with the naked eye or low-power magnification and can reveal features like the fracture type, origin, and secondary cracks. Microfractography uses higher magnification microscopy to study details like dimple shapes that indicate the fracture mode. Examples are given of using scanning electron microscopes to analyze ductile and brittle fracture surfaces at the microscopic level.
Fractured specimens must be carefully preserved and handled to prevent damage. The fracture surface should be coated immediately using dry air, desiccants, or transparent coatings like oil, grease or acrylic lacquers. These coatings protect the surface from environmental damage but must be completely removable without harming microstructural features. Various cleaning techniques can then be used to remove deposits from the fracture surface, such as using solvents, detergents, cathodic electrolysis or chemical etching, with the goal of revealing important microscopic details without introducing new damage.
The document outlines the procedure for analyzing a fracture that has occurred in a part or component. The key steps include:
1. Initial observation of the failed part to document details and ask questions about how it was used and maintained.
2. Laboratory studies to examine the material properties and microstructure of the part.
3. A synthesis of all the evidence including fracture surface analysis to determine the type of fracture, origin point, and likely causes.
The goal is to understand how and why the failure occurred by gathering background information and examining the part's material and fracture characteristics.
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Vacuum MEtallurgy Pressure and throughput distribution in vacuum systems
1. Pressure and Throughput Distribution in Vacuum Systems
By Howard Tring
Last time the discussion was about throughput and conductance in vacuum systems. This time we will look at
the pressure profile throughout the vacuum system in a slightly different way than it was shown last time. The
first thought might be that once the vacuum system is under vacuum carrying out the process, the lowest
pressure will be in the vacuum chamber and that the highest pressure will be at the primary pump exhaust
which will be atmospheric pressure. As we see from Fig. 1, this is not quite correct.
Fig. 1 shows how the pressure changes through the
system and actual values of P pressure and S speed
are given in the table, Fig. 2. The pressures shown
assume that the chamber has been evacuated
(pumped down) to the process pressure needed and
conditions are stable.
The graph shows values of throughput Q, pressure P
and pumping speed S at four points in the system.
The dotted lines indicate the point where the values
occur in this example. As was stated last time,
throughput Q is constant at any point in the system.
That means that as pressure P changes in one
direction pumping speed S must change in the other
direction as Q is constant.
Although the graph shows P1 at the chamber outlet
to the vacuum pumps, let’s start at P2 the inlet to the
diffusion pump. In North America the American Vacuum Society (AVS) measures diffusion pump pumping
speeds at the inlet flange in liters per second (l/sec or l sec-1) , in Europe these speeds are measured one radius
above the pump inlet and as a result are slightly lower. For a vacuum system manufacturer it means that they
should be cautious when comparing the rated speed of a USA made diffusion pump against one made in
Europe.
At Q2 = S2 P2, the inlet to the diffusion pump, the pumping speed is shown as 600 l/sec and the pressure is
indicated as 2.0 x 10-6 Torr. As we discussed last time, conductance through piping and accessories reduces the
effective pumping speed so the effective pumping speed in the vacuum chamber will be lower than at the
pump inlet.
When we lookat the table for values atQ1 = S1 P1 atthe outletof the chamber we see thatthe effective pumping
speed has dropped to 200 l/sec due to conductance losses through the piping and the high vacuum valve, and
the pressure is higher at 6 x 10-6 Torr.
This shows why the vacuum piping should be as short as possible, to minimize conductance losses. In an
efficient design the high vacuum valve and diffusion pump would be mounted as close as possible to the
chamber outlet flange. In the case of chambers where the diffusion pump can’t be mounted underneath, the
rightangle high vacuumvalve is mounted directlyto the chamber outletflange, and the diffusionpump directly
Fig. 1. Pressure & Throughput in a vacuum
system.
2. below the valve. In some case a cold trap is mounted between the high vacuum valve and the diffusion pump.
(Cold traps will be discussed in a month or two.)
Returning to position 2, the inlet to the diffusion pump, and following the pressure line into the diffusion pump
we see the following. There is a slight pressure drop towards the top jet of the jet assembly, which is the lowest
pressure shown in this representation. Then, as the gas stream passes the top jet, it is compressed to a higher
pressure between the two jets. At the second jet there is another small pressure drop as the gas molecules
become entrained in the oil vapor jet and then the vapor jet compresses the gas stream to the pressure at
which it is exhausted towards the primary pump. At this point the graph shows Q3 = S3 P3. From the table the
value of S3 is shown 0.06 l/sec (or 3.6 l/min) and the pressure is now up to 2.0 x 10-2 Torr. Pressure P3 is about
what would be expected in the foreline of the primary vacuum pump.
The next section of the pressure line
indicates a gradual pressure drop in the
foreline until the gas stream reaches the
inlet of the primary pump, position 4. In
most heat treating furnaces the primary
pump will be either an oil sealed rotary
piston or rotary vane pump. Depending on
the size of the furnace these pumps may
also have a Roots design vacuum booster mounted on the inlet. The vacuum booster pump develops a very
high pumping speed in the pressure range from about 30 Torr to 10-2 Torr. This is the pressure range where
most of the water vapor is released from the chamber, hot zone and product surfaces.
At position 4, where Q4 = S4 P4, the pumping speed S4 is shown in the table as 1.2 l/sec (72 l/min) and pressure
P4 is shown as 1.0 x 10-3 Torr. This would indicate that the pump used in this example is a two stage rotary vane
pump rather than a single stage rotary piston pump that has an ultimate vacuum of about 1 x 10-2 Torr (10
microns).
The final part of the pressure line then shows an initial pressure drop on the inlet side of the rotary vane pump
as the gas expands into the void between the rotor and stator, and then a pressure rise as the gas is isolated,
compressed up to atmospheric pressure and expelled from the pump on the outlet side of the mechanism.
Following through these steps shows that there are a number of pressure changes through the system as the
gas molecules are pumped from the vacuum chamber to atmospheric pressure at the primary pump exhaust.
References:
The two figures used in this discussion are taken from the textbook “Modern Vacuum Practice” (3rd edition,
page 70) written and published in the UK by Nigel Harris. Both have been slightly modified to show Torr units.
Howard Tring / Tel: (610) 792-3505 / E-
mail: HowardT@VacuumAndLowPressure.com / Web:www.vacuumandlowpressure.com
Howard Tring is the owner of Vacuum and Low Pressure Consulting, a company that supplies vacuum pump
accessories such as reconditioned inlet traps and exhaust filters and new replacement elements for exhaust
filters. Howard also offers on-site vacuum technology and oil sealed vacuum pump repair training and
Fig. 2. Pressure and Pumping Speed table.
3. consulting services, customized to the needs of the client. Howard is a member of ASM International and the
Heat Treat Society, the AVS, the SME, the SVC and the American Society for Training and Development.
Copyright December 2013, Tring Enterprises LLC - Comments on this article are welcome. I do not profess
to know everything about any specific vacuum related subject. However, I have worked in the vacuum pump
industry a long time and have seen good, bad and ugly. Please contact me with any comment or question. All
messages related to the content of the article will be answered.
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Conductance and Throughput in Vacuum Pipelines
By Howard Tring
Last month we discussed Gas Molecules and Gas Flow and at the end of the article mentioned the term
Conductance.
This time we will talk a bit more about conductance
in vacuum system piping and why it has to be taken
into consideration in the design of a typical vacuum
furnace or similar vacuum system. Firstly though, we
will discuss Throughput.
Throughput
Have you ever wondered why vacuum pipes and
connections are of several different sizes on any
vacuum system? I would suggest that most users
don’t really give it any thought. It is what it is. So let’s
look at the sections of a vacuum system and again try
to visualize those gas molecules, which are so tiny we
can’t see them, and understand the conditions at
different places in the system.
Pumping speed of large mechanical vacuum pumps is usually indicated in cubic feet per minute. That can be
denoted in several ways; cfm, cu ft /min or ft3 min-1. This is also shown in metric terms as cubic meters/hour,
liters/min and l/min also shown as m3 hr-1and l min-1.
Although the last terms are the most modern, in training I tend to use “cfm” and “l/min” as easy terms to write,
and not to use negative powers of ten. In this case the “-1” denotes that time is the divisor, under the line, in
the written equation or formula, i.e. per unit time, but some students who are new to vacuum technology or
engineering terms thinkofnegative powers oftenas a vacuumor a reading ofpressure lowerthanatmospheric
pressure.
So pumping speed units indicate the volume of gas being pumped in a certain time, but they do not relate that
pumping speed to any pressure term. If the pressure term is added then we can determine the mass of gas that
is flowing at that point in the system.
The formula for throughput is Q = P V / t = PS
Where Q = throughput, P = pressure, V = volume, S = pumping speed and t = time
Fig. 1. Throughput in a Vacuum Furnace.
4. Throughput is a constant at any point in the vacuum system, during normal operation. (Fig. 1) In this example I
have assigned a pumping speed “S” for the diffusion pump of 8000 l/sec. That makes the diffusion pump inlet
diameter about 20 inches (about 500 mm). The vacuum chamber pressure “P” is shown as 1 x 10-6 Torr which is
a typical pressure for manyvacuumapplications. (Remember that1 x 10-6 represents a 1 millionthpartof1 Torr)
At position 1, the high vacuum pump inlet, the product of P and S show a throughput Q of 4.8 x 10-1 Torr l/min.
At position 2, in the backing line at the exhaust of the diffusion pump, the pump has compressed the gas to 5 x
10-2 Torr, because we know that Q is constant at 4.8 x 10-1 Torr l/min we can calculate P which is 9.6 x 100 l/min.
At position 3, the gas from the backing line has been compressed through the mechanical vacuum pump to
atmospheric pressure 760 Torr, and as Q is 4.8 x 10-1 Torr l/min, P is calculated to be 6.3 x 10-4 l/min.
The gas, in the vacuum chamber at 1 x 10-6 Torr, (position 1) is in molecular flow, where the gas molecules move
in a random direction and collide more frequently with surfaces inside the chamber than they do with other
molecules. The pumping speed is entirely dependent on the inlet size of the diffusion pump; the larger the
pump inlet, the more gas molecules will enter the pump.
As the gas molecules pass through the vapor jets of the diffusion pump they are compressed to a smaller
volume and higher pressure, as shown in the backing line (position 2). At a pressure of about 5 x 10-2 Torr the
gas molecules are now in transition from molecular flow to viscous or continuum flow. (This backing line may
have a 3 to 6 inch diameter depending on the combination of diffusion and mechanical pumps used.)
The gas molecules in transitional flow now move down the pipeline to the lower pressure generated at the inlet
of the mechanical backing pump where they are compressed again, up to atmospheric pressure, and exhausted
from the system (position 3).
From this example we learn a bit more about gas molecules moving through the vacuum furnace system. At a
low pressure in the vacuum chamber a huge volume ofgas is first compressed in the diffusion pump by a factor
of about 10,000 times, from 1 x 10-6 up to 1 x 10-2 Torr. That gas is then compressed about another 15,000 times
in the mechanicalpump allowing itto be exhausted into the air at760 Torr. Neither vacuumpump cancompress
the gas from the vacuum chamber pressure up to atmospheric pressure on its own, but working as two pumps
in series it can be done successfully.
The example shown starts at an already low pressure in the vacuum chamber. If we look at another set of
numbers with the vacuum chamber pressure at around 1 x 10-3 Torr, throughput Q would be 1000 times larger
at 4.8 x 102 which is 480 Torr l/min. Because P will remain in the same range at position 2 and the same at
position3, calculations showthe pumping speed S also about1000 times higher atthose places inthe pumping
system.
Conductance
The conductance between two points in a vacuum system is expressed as the quantity flow rate of gas flowing
through a device divided by the resulting pressure drop.
C per meter = Q / P1- P2 and is expressed in liters per second (l/sec)
Therefore, ifthe pipe being considered hasa lengthof2 meters, the conductance fromthe chartinFig.2 is divided
by 2 to give the total conductance.
There are differentformulae forcalculating valuesofconductance inviscous andmolecularflow. Inthis discussion
we are looking at the roughing line conductance which for the most part will be in transitional flow conditions.
5. Although the conductance can be calculated, it is
easier to read the conductance (per meter) off the
graph in Fig. 2 for the example we are looking at.
Conductance values are used to determine the
“effective” pump speed at the vacuum chamber,
which can be quite different from the “rated” pump
speed of the vacuum pump at its inlet connection.
This knowledge is used to select the correct size of
mechanical vacuum pump to rough out the vacuum
chamber in the required time.
The roughing line shown in Fig. 1 runs horizontally
from the side of the vacuum chamber and then an
elbow turns it downwards to run to the mechanical
vacuum pump inlet. There is always a roughing valve
in this pipeline to allow the roughing line to be
opened and closed as needed. The valve has its own
conductance rating and some manufacturers will show that in their valve literature. For this simple example we
will ignore the valve conductance and only consider the pipeline which may have a total length of 2 meters or
3 meters depending on the system design. We will look at both options to see the difference.
If the mechanical roughing and backing pump is similar to a Stokes 212, having a rated pumping speed (Sp) of
150 cfm, it will have an inlet size of 3 inches. That is close to the 70 mm pipe size shown on Fig. 2 so we will use
the values of conductance for the 70 mm pipe size on that graph. To complete the calculation we have to
express the pump speed (Sp) in l/sec. We multiply 150 cfm by the factor shown in Fig.3 which is 0.472 to give a
pump speed of 70.8 l/sec.
The conductance varies with pressure so we need to compare different pressures to try to visualize the “big
picture” – of gas molecules that we can’t see. The pressure used is the “average pressure” in the pipeline being
studied.
The first pressure to consider is 1 Torr as it is close to
the highest pressure on the Fig. 2 chart. (At pressures
above 1 Torr the higher values of conductance allow
lots of gas flow and the pump speed loss is much
lower.)
At an average pressure of 1Torr the 70 mm diameter
pipe shows a conductance of 3,000 l/sec (per meter).
[Fig.2 black arrows]
The formula for calculating the effective pump speed (Se) is:
Se = Sp x C / Sp + C so it is quite simple now to fill in the relevant numbers and obtain the answer. Make sure
that the units used all match, you can’t mix cfm and l/sec.
So, at 1 Torr, for a 1 meter pipe, the formula becomes: Se = 70.8 x 3000 / 70.8 + 3000
That becomes: Se = 212,400 / 3070.8
Fig. 2. Conductance in pipes.
Fig. 3. Pump speed conversions.
6. And the effective speed at the chamber is: Se = 69.18 l/sec or 146 cfm.
So, if the roughing line is 70 mm bore and 1 m long, the effective pump speed Se at the chamber has only
dropped 4 cfm from the rated pumps speed Sp.
Now, looking at roughing lines of 2 m and 3 m length, we will see quite a difference.
For a roughing line of 2 m length, Se is 146 / 2 = 73 cfm
If the roughing line is 3 m long, Se is 146 / 3 = 49 cfm.
If we do the same calculations for the roughing line at an average pressure of 1 x 10-2 Torr, a 100 times lower
pressure, let’s see the results.
The conductance for a 1 m length pipe at 1 x 10-2 Torr
is 60 l/sec [Fig. 2 purple arrows] the calculation then
shows: Se = 68.9 cfm
For a roughing line of 2 m length, Se is about 35 cfm
If the roughing line is 3 m long, Se is about 23 cfm.
Either way, the results show a considerable loss of
pumping speed at the chamber inlet from the pump
inlet.
These numbers are tabulated in Fig. 4 to make them
easier to read.
In another article we can look at how conductance may affect pumping speed above the oil diffusion pump
and in the backing line.
Conclusions
For throughput: the pressures atdifferentpoints inthe systemshowthe veryhighcompressionratios developed
bythe oil diffusionpump and mechanicalpump. Compare themto the compressionratio ofa typicalcar engine
which is about 8 to 1.
For conductance: as the roughing line pressure drops below about 1 Torr the effective rough pumping speed
at the chamber is reduced considerably as the roughing line becomes longer, due to conductance losses in the
piping.
Roughing pipelines should be as short as possible, and as large a bore as practical.
Note: If the roughing line has an oversized bore to increase the conductance, it also adds extra volume to the
system that has to be evacuated. At some point the time needed to evacuate the added volume cancels out
the increased effective pump speed at the chamber and no improvement is seen.
Fig. 4. The effect of roughing line
conductance.